Pipe lagging material such as cloth and the like are used to provide protective coverings and insulation to pipe conduits. The material is generally composed of a base, such as a fabric, which is wrapped or "lagged" around either the outside insulation on a pipe in order to hold the insulation in place or the pipe itself in order to protect the contents of the pipe against thermal gain or loss. Such pipe lagging cloths are commonly applied to furnaces or boilers, electrical insulations and the like. It is desirable that such material be fireproof or flame-resistant and capable of withstanding high temperatures. It is further desirable that such material be safe to handle and possess sufficient adhesive properties to be retained on the pipe under various conditions of use.
Conventionally, lagging cloth is applied by itself directly to the component, or alternatively as an overlying wrap covering the thermal insulation placed about the component.
Most lagging material employed heretofore in the art has been formed of a material having an asbestos fiber base, and due to the health hazards normally associated with asbestos fibers, a need has arisen for an improved and safe high temperature material that could be used as a base for manufacturing pipe lagging material. The high temperature properties of glass fibers have led to the discovery that woven glass fabric provides a suitable pipe lagging product provided that a satisfactory coating meeting all the requirements of a rewettable adhesive is used in conjunction therewith.
Care must be taken in selecting a woven glass fabric that would not cause skin irritation, since the user of a rewettable pipe lagging material would come into intimate contact with the woven glass cloth during installation. It is also essential that the glass fabric have a high temperature coating which would be safe to handle, and at the same time, meet all the requirements of a rewettable lagging fabric. In manufacturing rewettable lagging fabric it is of prime importance that the material conform to irregular surfaces when wet, and possess sufficient dry and wet adhesion that the material adheres to the wrapped article. Safety and health considerations dictate that the material be non-flammable as well as non-toxic, and esthetic requirements require that the material possess a smooth white attractive outer surface after application so as to necessitate only a minimum of painting in order to achieve water-proofness. Furthermore, the pipe lagging materials should possess non-ravelling properties and be non-corrosive when used in combination with stainless steel.
The prior art has developed a number of materials, none of which heretofore have successfully met all the requirements as outlined above. For example, we have found that the product described in U.S. Pat. No. 3,839,079 does not form a satisfactory pipe lagging fabric since the material contains insufficient coating to give a smooth surface and the composition of the adhesive is such that it is impossible to apply enough coating to fill all the interstices of the fabric. A further short coming of the material described in U.S. Pat. No. 3,839,079 resides in the fact that the glass yarns are designated as long staple strands of glass fibers as disclosed in U.S. Pat. Nos. 2,584,517, 2,621,444, and 3,425,204. The yarn described in these later three patents is composed of staple glass fibers having a diameter in the range of 0.00028 inches and greater, and are known to cause irritation when in contact with the skin.
U.S. Pat. No. 3,769,072 describes a pipe lagging material which is primarily an asbestos base material noted for its flexibility and drapeability both in the dry and wet state. The reference also alludes to a porous base made of various other fibers such as cellulose, synthetic, proteinaceous, mineral, glass, asbestos, ceramic, and siliceous. Contrary to the description set forth in U.S. Pat. No. 3,769,072, we have found that when the adhesive composition described therein is applied to a woven fiberglass fabric, the resultant product is not a flexible and drapable product, but rather is a rigid, stiff product that does not lend itself readily to application as a pipe lagging material.
We have now found that the short comings of the prior art fabrics can be overcome by employing a base fabric and adhesive coating formulation according to the present invention. Accordingly, it is the primary object of the present invention to provide a glass fabric and a high temperature coating that is safe to handle and at the same time meets all the requirements of a rewettable lagging fabric, such as ability to conform to an irregular surface when wet and possess dry and wet adhesion to adhere to the wrapped article.
It is a further object of the present invention to provide a composition suitable for producing a pipe lagging material which possesses a smoth white attractive outer surface after application so as to require a minimum of painting and maintenance.
A still yet further object of the present invention is to provide a method for providing an improved pipe lagging material of the type hereinbefore indicated.